Structure and reactivity of bimetallic Ni-Au catalysts for syngas production and utilization

A key issue regarding the use of Ni catalysts for hydrocarbon steam reforming is their stability against carbon deposition. This deposition can be retarded by addition of promoter atoms such as Au that are thought to reside at the coordinatively unsaturated step and kinks sites. We have characterized the structure of Au-promoted Ni catalysts and investigated their reactivity toward syngas production and consumption. XPS and chemisorption results suggest the formation of a surface Au-Ni alloy. Methane steam reforming shows an effect of Au surface alloying through a modest reduction in initial activity and deactivation rate. However, CO DRIFT and methanation studies show little effect of Au addition. These latter results are consistent with surface reconstruction in the presence of CO, which minimizes the impact of Au. This study points out the contrast in findings from different characterization methods, and emphasizes the importance of characterizing bimetallic catalysts under actual working conditions.